Your computer must
Run some variant of a UNIX® operating system.
Have a standard user-shell (e.g., sh(1), ksh(1), bash(1)) .
Have sufficient local disk-space for the LDM product-queue, which can range from a few megabytes to many gigabytes in size - depending on your data requirements.
Have perl 5 installed.
Have the uptime, vmstat, netstat, and top utilities installed if you wish to collect metrics on the performance of the LDM system via the ldmadmin addmetrics command.
Have the gnuplot utility installed if you wish to plot metrics on the performance of the LDM system via the ldmadmin plotmetrics command, or the plotMetrics utility.
Have an accurate and monotonic clock.
The last requirement is absolutely necessary because the LDM protocol depends on accurate clocks on both the upstream host and the downstream host.
Additionally, if the clock is not monotonic (because it is periodically
set backwards by ntpdate(8), for example) then processes
that read from the product-queue (such as upstream LDMs and pqacts will miss some data-products that are in
the queue. This is because data-products reside in the product-queue in
the order in which they were inserted into the queue according to
the system clock. If the system clock jumps backwards, then a
data-product might not be inserted at the tail
of the queue and so be missed by a process waiting at the tail
for the next product. The rate at which products will be missed
depends, among other things, on the rate at which products are inserted
into the queue, the frequency with which the system clock is adjusted
backwards, and the amount of the adjustments.
Linux systems with kernels older than 2.6.18 (for 32-bit systems) or 2.6.21 (for 64-bit systems) are at high-risk for non-monotonic system clocks.
This requirement can be generally satisfied by running a Network Time Protocol daemon (ntpd). The NTP daemon is available at ntp.org. Information on public NTP time servers is available at http://ntp.isc.org/bin/view/Servers/WebHome. Linux users with the older kernels mentioned above should pay particular attention to the NTP support documentation on Known Hardware Issues and Known Operating System Issues.
You must have a UNIX® development-environment. In particular, your platform must have:
A Standard C compiler (e.g.,
c89(1)).
A standard make(1) utility.
While every effort is made to ensure that the LDM source-code distribution can be compiled and installed on as wide a variety of UNIX® platforms as possible, we can, necessarily, only test on platforms that are available at the Unidata Program Center (UPC).
With that in mind, here are tables of successful build environments and unsuccessful build environments.
The UPC reserves the right to deny support to outdated or irregular platforms.